Not applicable.
Not applicable.
1. Field of the Invention
The present invention generally relates to a battery-powered electronic device. More particularly, the invention relates to a power management protocol in which various system functions can be prioritized when the system conserves power.
2. Background of the Invention
Most every computer system with a rechargeable battery uses an external AC to DC converter (sometimes called an xe2x80x9cadapterxe2x80x9d) which converts the AC line voltage to a lower DC voltage. Due to its size, the adapter has often been referred to as the xe2x80x9cbrick.xe2x80x9d The brick is usually external to the computer shell and is often an awkward part of the system to store and carry. While using AC power, the brick supplies power both for the normal operation of the computer and also for recharging the battery.
Typical AC/DC converters are provided with an input of 100 to 240 VAC and generate an output voltage of 18 VDC with a total power output capacity of 50 to 70 watts. The size (i.e., power capacity) of the AC adapter is normally established by estimating a reasonable xe2x80x9cpower budgetxe2x80x9d for the CPU. The power budget is a total of the maximum power consumption of the computer""s internal devices (the CPU, core chipset, LCD panel, hard drive, etc.) plus some allocation for externally powered devices (e.g., USB, PS/2, or external storage). As discussed below, sometimes the power required for charging the battery is added to the power budget.
Older notebook computers with small LCD screens and low power processors typically consumed a maximum of 10 or 15 watts while operational. Today""s notebooks, however, with 15xe2x80x3 high resolution screen, multiple internal storage drives, and gigahertz processors can easily consume 50 to 60 watts of power. Moreover, performance requirements have demanded bigger AC/DC adapters which are designed to be sufficient for the worst case power consumption of the system.
While the power demands for portable computers continuously increases, the pressure to make the system xe2x80x9cmobilexe2x80x9d places pressure on the system designer to make the AC/DC brick as small as possible. Ergonomics discourages large AC/DC adapters which dissipate proportionately more heat. Further, cost pressures prohibit the use of more powerful or more efficient AC/DC bricks. Yet, at the same time, it is desirable for the computer to be able to charge the battery as quickly as possible. In sum, many consumers desire portables that have high performance (e.g., fast CPUs, bright displays, etc.), recharge batteries very quickly, are lightweight and small, inexpensive, and do not become hot to the touch.
To date, the concession to AC/DC size has been to xe2x80x9cthrottlexe2x80x9d battery charge when the rest of the system is under full loading. In many older systems, the xe2x80x9cpower budgetxe2x80x9d and AC/DC adapter size were calculated by estimating the consumption of the computer""s devices, and then adding an amount of power allocated directly for recharging the internal battery. Today, the one common concession towards power budget allocation is that power for the recharge of the battery itself is not included. This means that most adapters today are rated to provide sufficient power for the system at full load but not charging the battery. Thus, notebooks today measure the core system power consumption and then allocate the remaining AC/DC power (if there is any remaining power) to charge the battery. Examples of these types of systems are the Compaq Armada xe2x80x9cconstant powerxe2x80x9d AC/DC converter computers (starting with the Armada 4000, 1500 and continuing until the Armada 7800) and xe2x80x9cconstant voltage AC adapterxe2x80x9d systems, as featured by Dell Computer""s xe2x80x9cExpressChargexe2x80x9d (U.S. Pat. No. 5,939,862). In these systems the power capability of the AC adapter is prioritized to maintain operation of the CPU and other core logic, and if there is any left over power, such power is allocated for battery charging. If there is no power in excess of the power required by the CPU and core logic, then the battery will not be charged.
Although generally satisfactory, such power management systems have two notable shortcomings. First, under heavy CPU usage, the power consumed by the notebook may nearly consume all of the power available from the AC adapter, so that little power is available for battery charging. This may cause the system to take an annoying long period of time (e.g., hours) to recharge the battery. Second, under worst case loading of the system, it is possible to exceed the power output capability of the AC/DC adapter. This can happen, for example, if an operator connects peripheral devices (e.g., PCMCIA cards, USB devices, etc.) that cause the total power consumption of the system to exceed the power rating of the AC adapter. Under such a condition, the AC adapter may xe2x80x9ccollapsexe2x80x9d thereby disabling its output power to the system which, in turn, causes the system to xe2x80x9ccrash.xe2x80x9d A solution to the aforementioned problems is needed.
The problems noted above are solved in large part by a power management scheme for a computer system that prioritizes battery charging. The scheme includes determining when the output of a power adapter, which powers a computer and a battery subsystem, has reached or is about to reach a threshold which may be the power budget for the computer system. When this happens, rather than throttling battery charging, the system throttles back an aspect of the computer (e.g., CPU speed, display brightness). This keeps the battery charging at a faster rate than would have occurred in conventional power management schemes. Determining when the power budget is about to be exceeded can be accomplished by measuring the output current of the adapter or by monitoring the charge on the battery.
In an alternative power management scheme, after the computer has been throttled back, if the power budget still is being exceeded or is about to be exceeded again, then battery charging can be throttled back. This alternative scheme thus provides a two-tiered throttling protocol. In yet another embodiment, battery charging can be throttled first, followed, if necessary, by computer throttling.
These and other advantages will become apparent upon reviewing the following disclosure.